1. Field of the Invention
The present invention relates to a novel cleaning composition for use in microelectronics manufacturing. More particularly, the present invention relates to a non-corrosive cleaning composition for removing plasma etch residues formed on wafer substrates after plasma etching of metal layers or dielectric material layers deposited on the substrates.
2. Brief Description of the Prior Art
In the manufacture of microcircuits, photoresists are used as an intermediate mask for transferring an original mask pattern of a reticle onto wafer substrates by means of a series of photolithography and plasma etching steps. One of the final steps in the microcircuit manufacturing process is the removal of the patterned photoresist films from the substrates. In general, this step is affected by one of two methods.
One method involves a wet stripping step in which the photoresist-covered substrate is brought into contact with a photoresist stripper solution that consists primarily of an organic solvent and an amine. However, stripper solutions cannot completely and reliably remove the photoresist films, especially if the photoresist films have been exposed to UV radiation and plasma treatments during fabrication. Some photoresist films become highly crosslinked by such treatments and are more difficult to dissolve in the stripper solution. In addition, the chemicals used in these conventional wet-stripping methods are sometimes ineffective for removing inorganic or organometallic residual materials formed during the plasma etching of metal or oxide layers with halogen-containing gases.
An alternative method of removing a photoresist film involves exposing a photoresist-coated wafer to oxygen-based plasma in order to burn the resist film from the substrate surface in a process known as plasma ashing. However, plasma ashing is also not fully effective in removing the plasma etching by-products noted above. Instead removal of these plasma etch by-products must be accomplished by subsequently exposing the processed metal and dielectric thin films to certain cleaning solutions.
In a typical process, an antireflective coating such as DUV 30® (Brewer Science) is spin coated onto a damascene thin film stack then baked. A photoresist film is then applied by spin coating on top of the antireflective coating and is then pre-exposure baked. The photoresist is pattern-wise exposed using ultraviolet radiation, post-exposure baked, then developed in a dilute aqueous alkaline developer solution and subsequently rinsed with de-ionized water and spun-dried. The developed pattern is then transferred by reactive ion etching into the lower layers of the substrate's film stack. The photoresist and remaining antireflective coating are removed by plasma ashing techniques. Unwanted residues remain on the substrate as a result of the plasma ashing process.
Metal substrates are generally susceptible to corrosion. For example, substrates such as aluminum, copper, aluminum-copper alloy, tungsten nitride, and other metals and metal nitrides will readily corrode by using conventional cleaning chemistries. This is due to the high alkalinity of the conventional cleaning solutions.
Therefore, there remains a need for new types of cleaning compositions for removing plasma etch residues from substrates. Additionally, there remains a need for such a cleaning composition that does not deleteriously affect the substrate. Further, there remains a need for such a cleaning composition that is aqueous-based, non-hazardous and will not harm the environment. All of these concerns are addressed by the cleaning composition of the present invention, which is not only non-corrosive, but is also capable of effectively removing fresh and aged residues from a substrate.